阅读说明：本技术 一种聚偏氟乙烯包覆微米铝复合粉体及其制备方法 (Polyvinylidene fluoride coated micron aluminum composite powder and preparation method thereof ) 是由 王传彬 覃梅 孙一 易卓然 罗国强 沈强 张联盟 于 2021-08-17 设计创作，主要内容包括：本发明提供了一种聚偏氟乙烯包覆微米铝复合粉体及其制备方法,制备方法包括步骤：将微米铝粉加入非溶剂,分散均匀得到微米铝粉/非溶剂分散液；将聚偏氟乙烯溶解于有机良溶剂中,制备PVDF/溶剂溶液；将PVDF/溶剂溶液滴加至微米铝粉/非溶剂分散液内,其中,PVDF/溶剂溶液与微米铝粉/非溶剂分散液具有预设温差,反应完成后进行抽滤、洗涤、干燥,即得到聚偏氟乙烯包覆微米铝复合粉体。本发明采用聚偏氟乙烯包覆微米铝,PVDF在高温下不仅可以与氧化层反应,也能与铝核反应,反应过程中产生的气体能阻止铝粉在应用过程中的团聚,从而有效激活铝粉的燃烧反应,提高其整体放热量。(The invention provides polyvinylidene fluoride coated micron aluminum composite powder and a preparation method thereof, wherein the preparation method comprises the following steps: adding the micron aluminum powder into a non-solvent, and uniformly dispersing to obtain a micron aluminum powder/non-solvent dispersion liquid; dissolving polyvinylidene fluoride in an organic good solvent to prepare a PVDF/solvent solution; and (3) dropwise adding the PVDF/solvent solution into the micron aluminum powder/non-solvent dispersion liquid, wherein the PVDF/solvent solution and the micron aluminum powder/non-solvent dispersion liquid have a preset temperature difference, and after the reaction is finished, carrying out suction filtration, washing and drying to obtain the polyvinylidene fluoride coated micron aluminum composite powder. The polyvinylidene fluoride is adopted to coat the micron aluminum, the PVDF can react with an oxide layer and an aluminum core at high temperature, and gas generated in the reaction process can prevent the aluminum powder from agglomerating in the application process, so that the combustion reaction of the aluminum powder is effectively activated, and the integral heat release quantity of the aluminum powder is improved.)

1. A preparation method of polyvinylidene fluoride coated micron aluminum composite powder is characterized by comprising the following steps:

s1, adding the micron aluminum powder into a non-solvent, and uniformly dispersing to obtain a micron aluminum powder/non-solvent dispersion liquid;

s2, dissolving polyvinylidene fluoride in an organic good solvent to prepare a PVDF/solvent solution;

and S3, dropwise adding the PVDF/solvent solution into the micron aluminum powder/non-solvent dispersion liquid, wherein the PVDF/solvent solution and the micron aluminum powder/non-solvent dispersion liquid have a preset temperature difference, and after the reaction is finished, carrying out suction filtration, washing and drying to obtain the polyvinylidene fluoride coated micron aluminum composite powder.

2. The method according to claim 1, wherein the average particle diameter of the micron-sized aluminum powder of step S1 is in the range of 4.5 μm to 5.5 μm.

3. The method according to claim 2, wherein the non-solvent of step S1 includes one or more of water, ethanol, ethyl acetate, and cyclohexane.

4. The method according to claim 1, wherein the good organic solvent in step S2 includes one of N-dimethylformamide, N-dimethylacetamide, carbonate and tetrahydrofuran, and the purity of the polyvinylidene fluoride is 99.9% or more.

5. The preparation method of claim 2, wherein the mass of the polyvinylidene fluoride in step S2 is 5-20% of the mass of the micron aluminum powder.

6. The preparation method according to claim 5, wherein the mass-to-volume ratio of the polyvinylidene fluoride to the good organic solvent in step S2 is in a range of 1:100 to 1: 500.

7. The method according to any one of claims 1 to 6, wherein the volume ratio of the micron-sized aluminum powder/non-solvent dispersion liquid and the PVDF/solvent solution in step S3 is in the range of 2:1 to 10: 1.

8. The method as claimed in claim 7, wherein the predetermined temperature difference in step S3 is in the range of 15 ℃ to 50 ℃.

9. A polyvinylidene fluoride-coated micron aluminum composite powder characterized by being prepared by the method for preparing the polyvinylidene fluoride-coated micron aluminum composite powder according to any one of claims 1 to 8.

10. The polyvinylidene fluoride-coated micrometer aluminum composite powder of claim 9, wherein the polyvinylidene fluoride-coated micrometer aluminum composite powder is of a core/shell structure, the micrometer aluminum powder is a core, and the polyvinylidene fluoride-coated micrometer aluminum powder is coated on the surface of the micrometer aluminum powder by a shell.

Technical Field

The invention relates to the technical field of composite materials, and particularly relates to polyvinylidene fluoride coated micron aluminum composite powder and a preparation method thereof.

Background

The aluminum powder has the excellent characteristics of high density, high combustion enthalpy, wide sources, low price, quick reaction and no toxicity, and is widely used in the application fields of high-energy explosives, solid propellants, infrared bait bullets, thermites and the like. The addition of aluminum powder to energetic materials improves the combustion performance of these materials.

Aluminum easily reacts with air in the air to generate a layer of compact oxide film, and the oxide film can protect internal active aluminum from oxidation and can cause the problems of high ignition temperature, serious ignition delay and the like of aluminum powder in the actual use process, thereby seriously affecting the release rate of energy. Therefore, it is necessary to modify the aluminum powder to improve its performance and accelerate the application of the aluminum powder in energetic materials. In the existing research, a layer of compact substance is coated on the surface of aluminum powder to prepare composite particles with a core/shell structure, and the coating layer can keep the content of active aluminum, prevent further oxidation and is also beneficial to storage in a natural environment.

The fluorine-containing high molecular polymer has stable chemical properties, good weather resistance at normal temperature, and is not easy to oxidize and hydrophobic. How to apply fluorine-containing high molecular polymer to wrapping aluminum powder to solve the problems of insufficient combustion, low heat release and low reaction rate of the existing micron aluminum powder in air is the current research direction.

Disclosure of Invention

In view of the above, the invention aims to overcome the defects of the prior art, and provides a polyvinylidene fluoride coated micron aluminum composite powder and a preparation method thereof, so as to solve the problems of insufficient combustion, low heat release and low reaction rate of the existing micron aluminum powder in air.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a preparation method of polyvinylidene fluoride coated micron aluminum composite powder comprises the following steps:

s1, adding the micron aluminum powder into a non-solvent, and uniformly dispersing to obtain a micron aluminum powder/non-solvent dispersion liquid;

s2, dissolving polyvinylidene fluoride in an organic good solvent to prepare a PVDF/solvent solution;

and S3, dropwise adding the PVDF/solvent solution into the micron aluminum powder/non-solvent dispersion liquid, wherein the PVDF/solvent solution and the micron aluminum powder/non-solvent dispersion liquid have a preset temperature difference, and after the reaction is finished, carrying out suction filtration, washing and drying to obtain the polyvinylidene fluoride coated micron aluminum composite powder.

Alternatively, the particle size of the micron aluminum powder in step S1 is in the range of 4.5 μm to 5.5 μm.

Optionally, the non-solvent of step S1 includes one or more of water, ethanol, ethyl acetate, and cyclohexane.

Optionally, the good organic solvent in step S2 includes one of N-dimethylformamide, N-dimethylacetamide, carbonate and tetrahydrofuran, and the purity of the polyvinylidene fluoride is above 99.9%.

Optionally, in step S2, the mass of the polyvinylidene fluoride accounts for 5% to 20% of the mass of the micron aluminum powder.

Optionally, in step S2, the mass-to-volume ratio of the polyvinylidene fluoride to the good organic solvent is in a range from 1:100 to 1: 500.

Optionally, the volume ratio of the micron aluminum powder/non-solvent dispersion liquid and the PVDF/solvent solution in step S3 is in the range of 2:1 to 10: 1.

Optionally, the preset temperature difference in step S3 is in the range of 15 ℃ to 50 ℃.

The invention also aims to provide polyvinylidene fluoride-coated micron aluminum composite powder, which is prepared by the preparation method of the polyvinylidene fluoride-coated micron aluminum composite powder.

Optionally, the polyvinylidene fluoride-coated micron aluminum composite powder is of a core/shell structure, the micron aluminum powder is a core, and the polyvinylidene fluoride is coated on the surface of the micron aluminum powder by a shell.

Compared with the prior art, the polyvinylidene fluoride coated micron aluminum composite powder and the preparation method thereof provided by the invention have the following advantages:

(1) the polyvinylidene fluoride coated micron aluminum composite powder provided by the invention is of a core/shell structure and has good weather resistance, stability and dispersibility, Al is used as a core, and PVDF is used as a coating layer on the surface of micron Al, so that the oxidation of aluminum powder can be effectively prevented, and the activity of the aluminum powder can be maintained for a long time.

(2) The polyvinylidene fluoride is adopted to coat the micron aluminum, the PVDF can react with an oxide layer and an aluminum core at high temperature, and gas generated in the reaction process can prevent the aluminum powder from agglomerating in the application process, so that the combustion reaction of the aluminum powder is effectively activated, and the integral heat release quantity of the aluminum powder is improved.

(3) The preparation method is simple, has low requirement on equipment, is convenient to operate, has low cost and short period, and can be used for batch preparation.

Drawings

In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 is SEM images of PVDF @ u-Al composite powder of example 1 of the present invention at different magnifications;

FIG. 2 is a TG diagram of PVDF @ Al composite powder and aluminum powder in example 1 of the present invention;

FIG. 3 is a DSC chart of the PVDF @ Al composite powder and the aluminum powder in example 1 of the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

In the description of the present invention, it should be noted that the terms "first" and "second" mentioned in the embodiments of the present invention are only used for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

In the description of embodiments of the present application, the description of the term "some embodiments" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. Throughout this specification, the schematic representations of the terms used above do not necessarily refer to the same implementation or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

It should be noted that the term "in.

The particle size, surface morphology, oxide layer state and other factors of the aluminum powder have great influence on the energy release characteristics, wherein the particle size is the main factor influencing the combustion performance. The burning rate and the pressure index are improved to a certain extent by reducing the granularity of the aluminum powder (using nano aluminum powder), and the heat release is increased. However, simply reducing the particle size of the aluminum powder causes a significant problem: firstly, the nano aluminum powder has higher surface energy due to the increase of the specific surface area, and the aluminum powder can generate a stable chemical inert compound Al under the action of oxygen in the air₂O₃Leading to the reduction of the content of active aluminum in the nano aluminum powder; and secondly, an oxide layer on the surface of the nano aluminum powder is compact, poor in thermal conductivity and high in melting point, so that the transfer of heat to the active aluminum is limited, and the contact of the active aluminum and an oxidant is also hindered, so that the aluminum powder containing the oxide layer is not easy to ignite. This is also one of the causes of energy loss of the aluminum-containing composite energetic material.

Therefore, how to effectively maintain the activity of the nano aluminum powder and improve the combustion heat release efficiency is a core problem of the application of the nano aluminum powder in the field of composite energetic materials.

In order to solve the problems, the invention provides a preparation method of polyvinylidene fluoride coated micron aluminum composite powder, which comprises the following steps:

s1, adding the micron aluminum powder into a non-solvent, and uniformly dispersing to obtain a micron aluminum powder/non-solvent dispersion liquid;

s2, dissolving polyvinylidene fluoride in an organic good solvent to prepare a PVDF/solvent solution;

s3, dripping the PVDF/solvent solution into the micron aluminum powder/non-solvent dispersion liquid, wherein the PVDF/solvent solution and the micron aluminum powder/non-solvent dispersion liquid have a preset temperature difference, and after the reaction is finished, carrying out suction filtration, washing and drying to obtain the polyvinylidene fluoride coated micron aluminum composite powder PVDF @ u-Al.

It can be understood that the fluorine-containing polymer material generally has good weather resistance, aging resistance and radiation resistance in natural environment, and can be compounded with the nano aluminum powder by utilizing the characteristic of the fluorine-containing polymer material so as to achieve the purposes of reducing the content of active aluminum in the micron aluminum powder and preventing the active aluminum from being oxidized.

The embodiment of the invention adopts polyvinylidene fluoride (PVDF) to coat micron aluminum, the PVDF can react with an oxide layer at high temperature to generate loose and porous aluminum fluoride which becomes an oxygen transmission channel and can also react with an aluminum core, an Al-F pre-ignition reaction (PIR) exists to release certain heat, and gas generated in the reaction process can prevent the agglomeration of aluminum powder in the application process, so that the combustion reaction of the aluminum powder is effectively activated, and the integral heat release quantity of the aluminum powder is improved.

Specifically, in step S1, adding micron aluminum powder into a non-solvent, and performing ultrasound for several minutes at a certain power to obtain a uniformly dispersed micron aluminum powder/non-solvent dispersion liquid; wherein the non-solvent comprises one or more of water, ethanol, ethyl acetate and cyclohexane, and the particle size of the micron aluminum powder is in the range of 4.5-5.5 μm.

In step S2, PVDF which accounts for 5-20% of the mass of the micron aluminum powder is dissolved in the organic good solvent to prepare a uniform solution under the conditions of 40-60 ℃ and stirring at 1000-1500 rpm. Wherein the purity of the polyvinylidene fluoride is more than 99.9%. The good organic solvent comprises one of N-N-dimethylformamide, N-N-dimethylacetamide, carbonate and tetrahydrofuran.

The mass-to-volume ratio (g: ml) of the polyvinylidene fluoride to the good organic solvent is in the range of 1:100 to 1:500, and preferably, the mass-to-volume ratio of the polyvinylidene fluoride to the good organic solvent is 1: 300.

Specifically, in step S3, under the stirring condition of 800-1500rpm, the PVDF/solvent solution is slowly dropped into the micron aluminum powder/non-solvent dispersion liquid with temperature difference, after full reaction, the PVDF @ u-Al composite powder is obtained by suction filtration, washing and vacuum drying.

Wherein the volume ratio of the micron aluminum powder/non-solvent dispersion liquid to the PVDF/solvent solution is in the range of 2:1 to 5: 1. Preferably, the volume ratio of the micron aluminum powder/non-solvent dispersion to the PVDF/solvent solution is 3: 1.

Further, the predetermined temperature difference between the PVDF/solvent solution and the micron aluminum powder/non-solvent dispersion is in the range of 15 ℃ to 50 ℃. For example, the PVDF/solvent solution is 70 ℃ and the temperature of the micron aluminum powder/non-solvent dispersion is 20-55 ℃. The preset temperature difference is set because the solubility of PVDF increases with the temperature increase in a certain solubility range, and when the temperature of the micron aluminum powder/non-solvent dispersion liquid is lower than that of the PVDF/solvent solution, the PVDF is favorably precipitated and then coated on the surfaces of the aluminum powder particles.

In the embodiment of the invention, spherical micron aluminum powder is ultrasonically dispersed in a non-solvent of PVDF, the PVDF accounting for 5-20% of the mass of the micron aluminum powder is dissolved in an organic good solvent of the PVDF, and the micron aluminum powder is coated and modified by adopting a solvent non-solvent method to prepare the composite powder with uniform coating and a core/shell structure. The preparation method is simple, has low requirement on equipment, is convenient to operate, has low cost and short period, and can be used for batch preparation.

The invention further provides polyvinylidene fluoride-coated micron aluminum composite powder PVDF @ u-Al, which is prepared by the preparation method of the polyvinylidene fluoride-coated micron aluminum composite powder. The polyvinylidene fluoride-coated micron aluminum composite powder is of a core/shell structure, the micron aluminum powder is a core, and the polyvinylidene fluoride is coated on the surface of the micron aluminum powder.

The PVDF @ u-Al composite powder is of a core/shell structure, is good in weather resistance, stability and dispersibility, Al is used as a core, PVDF is used as a coating layer on the surface of micron Al, air can be effectively isolated, the influence of the environment on aluminum powder is relieved, the activity of the aluminum powder is kept for a long time, and the energy release characteristic is remarkably improved.

On the basis of the above embodiment, the following specific examples of the preparation method of the polyvinylidene fluoride-coated micron aluminum composite powder are given to further illustrate the invention. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are examples of experimental procedures not specified under specific conditions, generally according to the conditions recommended by the manufacturer. Unless otherwise indicated, percentages and parts are by mass.

Example 1

The embodiment provides a preparation method of polyvinylidene fluoride coated micron aluminum composite powder, which comprises the following steps:

1) weighing 1g of micron aluminum powder with the average particle size of 5um, adding the micron aluminum powder into 40ml of solution containing water and ethanol in a volume ratio of 1:1, and carrying out ultrasonic treatment for 30min at a power of 150w to obtain a uniformly dispersed micron aluminum powder suspension solution;

2) adding 0.08g of PVDF powder into 20ml of dimethylformamide solution, and stirring for 15min in a 40 ℃ water bath kettle at a stirring speed of 800rpm to obtain a completely dissolved PVDF/solvent solution;

3) and (3) dripping the PVDF/solvent solution into the micron aluminum powder suspension solution which is always in a stirring state (at room temperature) at the speed of 2ml/min, carrying out suction filtration and washing after dripping is finished, and drying the composite powder for 12 hours at the temperature of 50 ℃ under a vacuum condition to obtain the PVDF @ u-Al composite powder.

The PVDF @ u-Al composite powder prepared in example 1 was subjected to structural characterization by a scanning electron microscope, and a result graph shown in FIG. 1 was obtained. As can be seen from FIG. 1, PVDF can be effectively and uniformly coated on the surface of the micron aluminum powder, a core/shell structure is presented, and the composite powder has good dispersibility.

FIG. 2 is a thermogravimetric analysis TG graph of PVDF @ Al composite powder and aluminum powder, and it can be seen from FIG. 2 that the composite powder is heated from room temperature to 1300 ℃ at a heating rate of 10 ℃/min, and the heat release of the composite powder is 12090J/g, which is 1.84 times (6560J/g) of the raw aluminum powder

FIG. 3 is a differential scanning calorimetry DSC chart of the PVDF @ Al composite powder and the aluminum powder, and it can be seen from FIG. 3 that the temperature is increased from room temperature to 1300 ℃ at a heating rate of 10 ℃/min, the oxidation weight gain is 150.17%, which is 7.22% higher than that of the raw aluminum powder (the oxidation weight gain is 140.06%).

PIR (Pre-Ignition Reaction) refers to Al-F Pre-Ignition Reaction, and refers to Reaction of HF gas or low-molecular substances generated by decomposition of PVDF (polyvinylidene fluoride) under heating (about 330 ℃ under the air condition) and an oxide layer on the surface of aluminum powder, certain heat can be released in the Reaction process, the heat release of the main Reaction can be promoted to advance the Reaction, and the heat output of the optimized PIR can enhance the energy transmission.

Tests show that the initial reaction temperature of the PVDF @ u-Al composite powder pre-ignition reaction (PIR) is 357.9 ℃, the temperature is increased from room temperature to 1300 ℃ at a heating rate of 10 ℃/min, the heat release of the composite powder is 12090J/g, the composite powder is 1.84 times (6560J/g) of the raw aluminum powder, the oxidation weight gain is 150.17%, and the composite powder is improved by 7.22% compared with the raw aluminum powder (the oxidation weight gain is 140.06%).

In conclusion, the polyvinylidene fluoride coated micron aluminum composite powder prepared by the embodiment of the invention can prevent the aluminum powder from agglomerating in the application process by the gas generated in the reaction process, thereby effectively activating the combustion reaction of the aluminum powder and improving the overall heat release.

Example 2

The embodiment provides a preparation method of polyvinylidene fluoride coated micron aluminum composite powder, which comprises the following steps:

1) weighing 2g of micron aluminum powder with the average particle size of 5um, adding the micron aluminum powder into 60ml of solution containing water and ethanol in a volume ratio of 7:3, and carrying out ultrasonic treatment for 25min at the power of 200w to obtain uniformly dispersed micron aluminum powder suspension solution;

2) adding 0.2g of PVDF powder into 25ml of dimethylacetamide solution, and stirring for 30min in a 45 ℃ water bath kettle at a stirring speed of 900rpm to obtain a completely dissolved PVDF/solvent solution;

3) and (3) dripping the PVDF/solvent solution into the micron aluminum powder suspension solution which is always in a stirring state (at room temperature) at the speed of 3ml/min, carrying out suction filtration and washing after dripping is finished, and drying the composite powder for 10 hours at the temperature of 50 ℃ under a vacuum condition to obtain the PVDF @ u-Al composite powder.

Example 3

The embodiment provides a preparation method of polyvinylidene fluoride coated micron aluminum composite powder, which comprises the following steps:

1) weighing 3.5g of micron aluminum powder with the average particle size of 5um, adding the micron aluminum powder into 120ml of hexane solution, and carrying out ultrasonic treatment for 10min at the power of 300w to obtain a uniformly dispersed micron aluminum powder suspension solution;

2) adding 0.62g of PVDF powder into 50ml of dimethylacetamide solution, and stirring for 10min in a water bath kettle at 60 ℃ at a stirring speed of 1200rpm to obtain a completely dissolved PVDF/solvent solution;

3) and (3) dripping the PVDF/solvent solution into the micron aluminum powder suspension solution which is always in a stirring state (at room temperature) at the speed of 1ml/min, carrying out suction filtration and washing after dripping is finished, and drying the composite powder for 24 hours at the temperature of 55 ℃ under a vacuum condition to obtain the PVDF @ u-Al composite powder.

Example 4

The embodiment provides a preparation method of polyvinylidene fluoride coated micron aluminum composite powder, which comprises the following steps:

1) weighing 2.5g of micron aluminum powder with the average particle size of 5um, adding the micron aluminum powder into 70ml of acetone solution, and carrying out ultrasonic treatment for 15min at the power of 250w to obtain a uniformly dispersed micron aluminum powder suspension solution;

2) adding 0.375g of PVDF powder into 35ml of tetrahydrofuran solution, and stirring for 20min in a 50 ℃ water bath kettle at a stirring speed of 1000rpm to obtain a PVDF/solvent solution;

3) and (3) dripping the PVDF solvent solution into the micron aluminum powder suspension solution which is always in a stirring state (at room temperature) at the speed of 3ml/min, carrying out suction filtration and washing after dripping is finished, and drying the composite powder for 24 hours at the temperature of 55 ℃ under a vacuum condition to obtain the PVDF @ u-Al composite powder.

Example 5

The embodiment provides a preparation method of polyvinylidene fluoride coated micron aluminum composite powder, which comprises the following steps:

1) weighing 5g of micron aluminum powder with the average particle size of 5um, adding the micron aluminum powder into 300ml of ethanol solution, and carrying out ultrasonic treatment for 5min at the power of 350w to obtain a uniformly dispersed micron aluminum powder suspension solution;

2) adding 0.9g of PVDF powder into 80ml of ethylene carbonate, and stirring for 10min in a 70 ℃ water bath kettle at a stirring speed of 1500rpm to obtain a PVDF/solvent solution;

3) and (3) dripping the PVDF solvent solution into the micron aluminum powder suspension solution which is always in a stirring state (at room temperature) at the speed of 5ml/min, carrying out suction filtration and washing after dripping is finished, and drying the composite powder for 20 hours at the temperature of 65 ℃ under a vacuum condition to obtain the PVDF @ u-Al composite powder.

Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present disclosure, and these changes and modifications are intended to be within the scope of the present disclosure.